The disclosure concerns a method to operate a digital printer to print a recording material with toner particles that are applied with the aid of a liquid developer, in particular a high-speed printer to print web-shaped or sheet-shaped recording media. The disclosure also concerns a digital printer to execute the method.
In such digital printers, a latent charge image of a charge image carrier is inked by means of electrophoresis with the aid of a liquid developer. The toner image that is created in such a manner is transferred indirectly (via a transfer element) or directly to the recording medium. The liquid developer has toner particles and cleaning fluid in a desired ratio. Mineral oil is advantageously used as a cleaning fluid. In order to provide the toner particles with an electrostatic charge, charge control substances are added to the liquid developer. Further additives are additionally added, for example, in order to achieve the desired viscosity or a desired drying behavior of the liquid developer.
Such digital printers have been known for a long time, for example from DE 10 2010 015 985 A1, DE 10 2008 048 256 A1 or DE 10 2009 060 334 A1.
From the document US 2011/0286757 A1 (corresponding to DE 10 2010 017 005 A1), a method is known in which the toner concentration and the fill level in a mixing container are regulated to corresponding desired values via a regulatory arrangement. The desired value for the fill level is the same for all operating modes of the printer and has a relatively high value with regard to the maximum fill level of the mixing container. For example, the mixing container must be able to accommodate the entirety of developer fluid of the developer station connected to it, even in the operating case without active developer station, for which it must be designed to be relatively large in volume. In different operating modes, large volumes of developer fluid must additionally be recirculated with the aid of the regulatory arrangement, which can be problematic for the complete regulatory process, the toner concentration regulation, and therefore the print quality.